The discovery of hyperthermophilic archaebacteria has provided a valuable commercial and research tool. The intrinsic thermal stability of the enzymes isolated from these sources is maintained without any components unique to thermophiles, suggesting that the increase in molecular stability is accomplished through the same stereochemical interactions found in their mesophilic counterparts. The characteristic range of activity observed in hyperthermophilic enzymes tends to parallel growth temperature, there being little or no activity at temperatures which would be optimal for their mesophilic counterparts.
Alpha-amylases are of industrial importance and thus this enzyme is a popular subject for study. Alpha-amylases have been purified from a variety of species spanning the range of thermostability from mesophiles (Takagi et al, Bacterial and Mold Amylases The Enzymes, New York, Academic Press (1971), moderate thermophiles (Antranikian, Applied Biochemistry and Biotechnology 20/21:267-279 (1989); Glymph et al, Applied and Environmental Microbiology 34(4):391 (1977)); Hasegawa et al, J. Biochem. 79:35-42 (1976)) to hyperthermophiles (Koch et al, Arch. Microbiol. 155:572-578 (1991); Schumann et al, FEBS Letters. 282(1): 122-126 (1991)).
Pyrococcus furiosus is an anaerobic marine heterotroph with an optimal growth temperature of 100.degree. C., isolated by Fiala and Stetter from solfataric mud off the coast of Vulcano Island, Italy (Fiala et al, Arch. Microbiol. 145:56-61 (1986)). Alpha-amylase activity has been reported in the cell homogenate and growth medium of P. furiosus (Brown et al, Applied and Environmental Microbiology. 56(7):1985-1991 (1990); Koch et al, FEMS Microbiology Letters. 71:21-26 (1990)) but purification of this enzyme has not been reported.
The present invention provides .alpha.-amylase from P. furiosus in purified form and a method of effecting that purification.